Homogeneity and Trend Analysis of Rainfall and Streamflow of Seyhan Basin (Turkey)

Abstract

Changes in the historical rainfall and streamflow observations are important for understanding the climate change. The homogeneity of the annual and monthly times series of 9 rainfall stations and 3 streamflow gages, located at the Seyhan basin in Turkey, was examined using standard normal homogeneity test and Buishand test. The trend was studied by Mann-Kendall test, which is used for identifying the significance of the trend, and the Sen’s slope estimator, which provides the magnitude of the trend. Finally, the Pettit test was also applied on the annual time series only to obtain the most probable change year. The entire time series was found as homogeneous, although several significant p values were obtained in the 0.05 but not in the 0.01 significance level. The annual trend varied from one station to another but was found to be significant in one rainfall and one streamflow station at the 0.1 significance level only. Monthly time series was found to have the most significant trend in January at 0.05 significance level. Several months have no stations with a significant trend, while others have only one station with a significant trend. The Pettit test results showed no consistent change year through all the stations, although the most frequent change year obtained was for 1981.